/**
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.apache.zookeeper;

import java.util.ArrayList;
import java.util.Deque;
import java.util.LinkedList;
import java.util.List;

import org.apache.zookeeper.AsyncCallback.VoidCallback;
import org.apache.zookeeper.common.PathUtils;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

public class ZKUtil {
	private static final Logger LOG = LoggerFactory.getLogger(ZKUtil.class);

	/**
	 * Recursively delete the node with the given path.
	 * <p>
	 * Important: All versions, of all nodes, under the given node are deleted.
	 * <p>
	 * If there is an error with deleting one of the sub-nodes in the tree, this
	 * operation would abort and would be the responsibility of the app to handle
	 * the same.
	 * 
	 * See {@link #delete(String, int)} for more details.
	 * 
	 * @throws IllegalArgumentException if an invalid path is specified
	 */
	public static void deleteRecursive(ZooKeeper zk, final String pathRoot)
			throws InterruptedException, KeeperException {
		PathUtils.validatePath(pathRoot);

		List<String> tree = listSubTreeBFS(zk, pathRoot);
		LOG.debug("Deleting " + tree);
		LOG.debug("Deleting " + tree.size() + " subnodes ");
		for (int i = tree.size() - 1; i >= 0; --i) {
			// Delete the leaves first and eventually get rid of the root
			zk.delete(tree.get(i), -1); // Delete all versions of the node with -1.
		}
	}

	/**
	 * Recursively delete the node with the given path. (async version).
	 * 
	 * <p>
	 * Important: All versions, of all nodes, under the given node are deleted.
	 * <p>
	 * If there is an error with deleting one of the sub-nodes in the tree, this
	 * operation would abort and would be the responsibility of the app to handle
	 * the same.
	 * <p>
	 * 
	 * @param zk       the zookeeper handle
	 * @param pathRoot the path to be deleted
	 * @param cb       call back method
	 * @param ctx      the context the callback method is called with
	 * @throws IllegalArgumentException if an invalid path is specified
	 */
	public static void deleteRecursive(ZooKeeper zk, final String pathRoot, VoidCallback cb, Object ctx)
			throws InterruptedException, KeeperException {
		PathUtils.validatePath(pathRoot);

		List<String> tree = listSubTreeBFS(zk, pathRoot);
		LOG.debug("Deleting " + tree);
		LOG.debug("Deleting " + tree.size() + " subnodes ");
		for (int i = tree.size() - 1; i >= 0; --i) {
			// Delete the leaves first and eventually get rid of the root
			zk.delete(tree.get(i), -1, cb, ctx); // Delete all versions of the node with -1.
		}
	}

	/**
	 * BFS Traversal of the system under pathRoot, with the entries in the list, in
	 * the same order as that of the traversal.
	 * <p>
	 * <b>Important:</b> This is <i>not an atomic snapshot</i> of the tree ever, but
	 * the state as it exists across multiple RPCs from zkClient to the ensemble.
	 * For practical purposes, it is suggested to bring the clients to the ensemble
	 * down (i.e. prevent writes to pathRoot) to 'simulate' a snapshot behavior.
	 * 
	 * @param zk       the zookeeper handle
	 * @param pathRoot The znode path, for which the entire subtree needs to be
	 *                 listed.
	 * @throws InterruptedException
	 * @throws KeeperException
	 */
	public static List<String> listSubTreeBFS(ZooKeeper zk, final String pathRoot)
			throws KeeperException, InterruptedException {
		Deque<String> queue = new LinkedList<String>();
		List<String> tree = new ArrayList<String>();
		queue.add(pathRoot);
		tree.add(pathRoot);
		while (true) {
			String node = queue.pollFirst();
			if (node == null) {
				break;
			}
			List<String> children = zk.getChildren(node, false);
			for (final String child : children) {
				final String childPath = node + "/" + child;
				queue.add(childPath);
				tree.add(childPath);
			}
		}
		return tree;
	}

}